It is certainly possible to find natural objects that appear to be artifacts.

Despite making such an objection, I agree. In fact, I had a long aside after the "oops", but figured short and sweet was better suited for Daniel... or at least better entertainment, since Daniel appears completely immune to reason.

There are obviously circumstances where we would conclude an artifact was made by non-human intelligence. Stonehenge on Mars might be subject to debate for a while (until we got a real good look at it) but if we found something like a MER rover, there wouldn't be any doubt. No one would say "gee... maybe that was assembled by a dust devil in a rock heap"

But as you say, this doesn't validate IDs "design detection" in biology. We, machine building humans, would have no trouble recognizing a MER-like artifact as designed. A 15th century craftsman would likely come to the same conclusion if he kept his superstitions in check, but an equally intelligent human from a stone age culture would have little to go on.